Over one million persons in the United States are aphasic subsequent to a stroke. Most of the individuals improve through spontaneous recovery and treatment. However, there are no precise methods for predicting which patients will improve and, for those who do, how much improvement will occur. There is a need to improve prognostic precision in aphasia. The purpose of this investigation is to test the precision of auditory evoked responses (AERs) to provide a prognosis for improvement in aphasia subsequent to a left hemisphere thromboembolic infarct. We hypothesize that the presence, absence, and pattern of the AER responses will predict severity of aphasia and prognosis for improvement. Phonemic, phonologic, semantic, and syntactic language tasks will be used to elicit AERs, including the auditory late response, the mismatch negativity response (MMN), the N400, and the P600.